1. Field of the Invention
High-pressure gaseous oxygen is typically utilized as the oxidizer in the bipropellant systems of many spacecraft as well as in various test systems in which gaseous oxygen is flowing. In many of these systems, gaseous oxygen at high pressures is often heated to elevated temperatures of 500-degrees Fahrenheit or more before the oxidizer is introduced at a selected flow rate into the combustion chamber of the spacecraft engine.
The present invention relates to new and improved valves for controlling high-pressure gases such as gaseous oxygen flowing at extreme temperatures as well as for various types of fluid systems where cryogenic fluids and abrasive fluids are flowing. More particularly, the invention is directed to new and improved flow controlling valves cooperatively arranged to be moved between operating positions without creating objectionable backpressure surges in the flow system upstream of the valves.
2. Background Art
Flow control valves are typically arranged for regulating the flow of various gases or liquids over selected ranges of flow conditions and fluid pressures and temperatures. With many types of control valves, it is preferred to arrange the flow passages through those valves to minimize disruptions or significant turbulence of those fluids which are passing through the valves. Generally, little consideration is given to the nature of the fluids which are to be regulated by a particular flow control valve unless those fluids are corrosive (e.g., an acid or a strong caustic) or the fluids are abrasive (e.g., a slurry of particulates such as carbon black or coal). It will, of course, be appreciated that these fluids are readily accommodated either by fabricating critical components of the control valves from appropriate plastics, ceramics or metals or by protecting the exposed surfaces of these components with suitable materials.
Heretofore there has been only a limited demand for flow control valves for specialized fluids such as gaseous oxygen at elevated temperatures and pressures. As a result, those skilled in the art will appreciate that prior-art control valves are generally not suited for such specialized fluids. Therefore, it was not until the advent of rocket propulsion systems that utilize gaseous bipropellants that the critical problems associated with these gaseous bipropellants were even considered much less adequately addressed.
In particular, it has been found that where a fluid such as gaseous oxygen at high pressure and elevated temperatures is to be controlled, the valve must be carefully designed to minimize the risk of violent combustion of the gases passing through the valve. For instance, where a given flow control valve has a tortuous flow passage, there is a serious risk that particulates entrained in gaseous oxygen flowing at high velocities through the valve may be spontaneously ignited by the impact of the particulates against flat surfaces or corners in the flow passage. Moreover, it has also been found that the risk of combustion of components of such valves is significantly increased by the presence of a few extremely-small contaminant particles of metal or the like in a high-velocity stream of gaseous oxygen flowing through a valve having a flow passage with only a minor change of direction or a portion that represents a modest transition zone. It will be appreciated, therefore, that these problems will be even greater in a multi-port control valve where the gaseous bipropellant is to be diverted from one outlet port of the control valve to another outlet port of the valve.
Tests have shown, for example, that when even a small number of metal particles which are no larger than 2,000-.mu.m (0.079-inch) in diameter are inadvertently being transported in a high-velocity stream of oxygen, the impact of those particles against opposing surfaces in the flow passages in conventional control valves can promote the combustion of the materials of the valve bodies and the other components of the fluid system. Thus, since it is impossible to completely eliminate the presence of such minute particles in the flow lines and propellant tanks, it is essential that every component in the fluid system be designed to minimize as far as possible the risk that the impact of one or more of these particles against an opposing surface in the flow passages in these valves will cause a violent combustion of the particles as well as the various components which are exposed to the propellant fluid.